bpf_filter.c revision 1.3
1 /*- 2 * Copyright (c) 1990-1991 The Regents of the University of California. 3 * All rights reserved. 4 * 5 * This code is derived from the Stanford/CMU enet packet filter, 6 * (net/enet.c) distributed as part of 4.3BSD, and code contributed 7 * to Berkeley by Steven McCanne and Van Jacobson both of Lawrence 8 * Berkeley Laboratory. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by the University of 21 * California, Berkeley and its contributors. 22 * 4. Neither the name of the University nor the names of its contributors 23 * may be used to endorse or promote products derived from this software 24 * without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 36 * SUCH DAMAGE. 37 * 38 * from: @(#)bpf_filter.c 7.2 (Berkeley) 5/14/91 39 * $Id: bpf_filter.c,v 1.3 1993/05/20 03:05:53 cgd Exp $ 40 */ 41 42 #include <sys/param.h> 43 #include <sys/types.h> 44 #include <sys/time.h> 45 #include <net/bpf.h> 46 47 #ifdef sun 48 #include <netinet/in.h> 49 #endif 50 51 #if defined(sparc) || defined(mips) || defined(ibm032) 52 #define BPF_ALIGN 53 #endif 54 55 #ifndef BPF_ALIGN 56 #define EXTRACT_SHORT(p) ((u_short)ntohs(*(u_short *)p)) 57 #define EXTRACT_LONG(p) (ntohl(*(u_long *)p)) 58 #else 59 #define EXTRACT_SHORT(p)\ 60 ((u_short)\ 61 ((u_short)*((u_char *)p+0)<<8|\ 62 (u_short)*((u_char *)p+1)<<0)) 63 #define EXTRACT_LONG(p)\ 64 ((u_long)*((u_char *)p+0)<<24|\ 65 (u_long)*((u_char *)p+1)<<16|\ 66 (u_long)*((u_char *)p+2)<<8|\ 67 (u_long)*((u_char *)p+3)<<0) 68 #endif 69 70 #ifdef KERNEL 71 #include <sys/mbuf.h> 72 #define MINDEX(m, k) \ 73 { \ 74 register int len = m->m_len; \ 75 \ 76 while (k >= len) { \ 77 k -= len; \ 78 m = m->m_next; \ 79 if (m == 0) \ 80 return 0; \ 81 len = m->m_len; \ 82 } \ 83 } 84 85 static int 86 m_xword(m, k, err) 87 register struct mbuf *m; 88 register int k, *err; 89 { 90 register int len; 91 register u_char *cp, *np; 92 register struct mbuf *m0; 93 94 len = m->m_len; 95 while (k >= len) { 96 k -= len; 97 m = m->m_next; 98 if (m == 0) 99 goto bad; 100 len = m->m_len; 101 } 102 cp = mtod(m, u_char *) + k; 103 if (len - k >= 4) { 104 *err = 0; 105 return EXTRACT_LONG(cp); 106 } 107 m0 = m->m_next; 108 if (m0 == 0 || m0->m_len + len - k < 4) 109 goto bad; 110 *err = 0; 111 np = mtod(m0, u_char *); 112 switch (len - k) { 113 114 case 1: 115 return (cp[k] << 24) | (np[0] << 16) | (np[1] << 8) | np[2]; 116 117 case 2: 118 return (cp[k] << 24) | (cp[k + 1] << 16) | (np[0] << 8) | 119 np[1]; 120 121 default: 122 return (cp[k] << 24) | (cp[k + 1] << 16) | (cp[k + 2] << 8) | 123 np[0]; 124 } 125 bad: 126 *err = 1; 127 return 0; 128 } 129 130 static int 131 m_xhalf(m, k, err) 132 register struct mbuf *m; 133 register int k, *err; 134 { 135 register int len; 136 register u_char *cp; 137 register struct mbuf *m0; 138 139 len = m->m_len; 140 while (k >= len) { 141 k -= len; 142 m = m->m_next; 143 if (m == 0) 144 goto bad; 145 len = m->m_len; 146 } 147 cp = mtod(m, u_char *) + k; 148 if (len - k >= 2) { 149 *err = 0; 150 return EXTRACT_SHORT(cp); 151 } 152 m0 = m->m_next; 153 if (m0 == 0) 154 goto bad; 155 *err = 0; 156 return (cp[k] << 8) | mtod(m0, u_char *)[0]; 157 bad: 158 *err = 1; 159 return 0; 160 } 161 #endif 162 163 /* 164 * Execute the filter program starting at pc on the packet p 165 * wirelen is the length of the original packet 166 * buflen is the amount of data present 167 */ 168 u_int 169 bpf_filter(pc, p, wirelen, buflen) 170 register struct bpf_insn *pc; 171 register u_char *p; 172 u_int wirelen; 173 register u_int buflen; 174 { 175 register u_long A, X; 176 register int k; 177 long mem[BPF_MEMWORDS]; 178 179 if (pc == 0) 180 /* 181 * No filter means accept all. 182 */ 183 return (u_int)-1; 184 #ifdef lint 185 A = 0; 186 X = 0; 187 #endif 188 --pc; 189 while (1) { 190 ++pc; 191 switch (pc->code) { 192 193 default: 194 #ifdef KERNEL 195 return 0; 196 #else 197 abort(); 198 #endif 199 case BPF_RET|BPF_K: 200 return (u_int)pc->k; 201 202 case BPF_RET|BPF_A: 203 return (u_int)A; 204 205 case BPF_LD|BPF_W|BPF_ABS: 206 k = pc->k; 207 if (k + sizeof(long) > buflen) { 208 #ifdef KERNEL 209 int merr; 210 211 if (buflen != 0) 212 return 0; 213 A = m_xword((struct mbuf *)p, k, &merr); 214 if (merr != 0) 215 return 0; 216 continue; 217 #else 218 return 0; 219 #endif 220 } 221 #ifdef BPF_ALIGN 222 if (((int)(p + k) & 3) != 0) 223 A = EXTRACT_LONG(&p[k]); 224 else 225 #endif 226 A = ntohl(*(long *)(p + k)); 227 continue; 228 229 case BPF_LD|BPF_H|BPF_ABS: 230 k = pc->k; 231 if (k + sizeof(short) > buflen) { 232 #ifdef KERNEL 233 int merr; 234 235 if (buflen != 0) 236 return 0; 237 A = m_xhalf((struct mbuf *)p, k, &merr); 238 continue; 239 #else 240 return 0; 241 #endif 242 } 243 A = EXTRACT_SHORT(&p[k]); 244 continue; 245 246 case BPF_LD|BPF_B|BPF_ABS: 247 k = pc->k; 248 if (k >= buflen) { 249 #ifdef KERNEL 250 register struct mbuf *m; 251 252 if (buflen != 0) 253 return 0; 254 m = (struct mbuf *)p; 255 MINDEX(m, k); 256 A = mtod(m, u_char *)[k]; 257 continue; 258 #else 259 return 0; 260 #endif 261 } 262 A = p[k]; 263 continue; 264 265 case BPF_LD|BPF_W|BPF_LEN: 266 A = wirelen; 267 continue; 268 269 case BPF_LDX|BPF_W|BPF_LEN: 270 X = wirelen; 271 continue; 272 273 case BPF_LD|BPF_W|BPF_IND: 274 k = X + pc->k; 275 if (k + sizeof(long) > buflen) { 276 #ifdef KERNEL 277 int merr; 278 279 if (buflen != 0) 280 return 0; 281 A = m_xword((struct mbuf *)p, k, &merr); 282 if (merr != 0) 283 return 0; 284 continue; 285 #else 286 return 0; 287 #endif 288 } 289 #ifdef BPF_ALIGN 290 if (((int)(p + k) & 3) != 0) 291 A = EXTRACT_LONG(&p[k]); 292 else 293 #endif 294 A = ntohl(*(long *)(p + k)); 295 continue; 296 297 case BPF_LD|BPF_H|BPF_IND: 298 k = X + pc->k; 299 if (k + sizeof(short) > buflen) { 300 #ifdef KERNEL 301 int merr; 302 303 if (buflen != 0) 304 return 0; 305 A = m_xhalf((struct mbuf *)p, k, &merr); 306 if (merr != 0) 307 return 0; 308 continue; 309 #else 310 return 0; 311 #endif 312 } 313 A = EXTRACT_SHORT(&p[k]); 314 continue; 315 316 case BPF_LD|BPF_B|BPF_IND: 317 k = X + pc->k; 318 if (k >= buflen) { 319 #ifdef KERNEL 320 register struct mbuf *m; 321 322 if (buflen != 0) 323 return 0; 324 m = (struct mbuf *)p; 325 MINDEX(m, k); 326 A = mtod(m, char *)[k]; 327 continue; 328 #else 329 return 0; 330 #endif 331 } 332 A = p[k]; 333 continue; 334 335 case BPF_LDX|BPF_MSH|BPF_B: 336 k = pc->k; 337 if (k >= buflen) { 338 #ifdef KERNEL 339 register struct mbuf *m; 340 341 if (buflen != 0) 342 return 0; 343 m = (struct mbuf *)p; 344 MINDEX(m, k); 345 X = (mtod(m, char *)[k] & 0xf) << 2; 346 continue; 347 #else 348 return 0; 349 #endif 350 } 351 X = (p[pc->k] & 0xf) << 2; 352 continue; 353 354 case BPF_LD|BPF_IMM: 355 A = pc->k; 356 continue; 357 358 case BPF_LDX|BPF_IMM: 359 X = pc->k; 360 continue; 361 362 case BPF_LD|BPF_MEM: 363 A = mem[pc->k]; 364 continue; 365 366 case BPF_LDX|BPF_MEM: 367 X = mem[pc->k]; 368 continue; 369 370 case BPF_ST: 371 mem[pc->k] = A; 372 continue; 373 374 case BPF_STX: 375 mem[pc->k] = X; 376 continue; 377 378 case BPF_JMP|BPF_JA: 379 pc += pc->k; 380 continue; 381 382 case BPF_JMP|BPF_JGT|BPF_K: 383 pc += (A > pc->k) ? pc->jt : pc->jf; 384 continue; 385 386 case BPF_JMP|BPF_JGE|BPF_K: 387 pc += (A >= pc->k) ? pc->jt : pc->jf; 388 continue; 389 390 case BPF_JMP|BPF_JEQ|BPF_K: 391 pc += (A == pc->k) ? pc->jt : pc->jf; 392 continue; 393 394 case BPF_JMP|BPF_JSET|BPF_K: 395 pc += (A & pc->k) ? pc->jt : pc->jf; 396 continue; 397 398 case BPF_JMP|BPF_JGT|BPF_X: 399 pc += (A > X) ? pc->jt : pc->jf; 400 continue; 401 402 case BPF_JMP|BPF_JGE|BPF_X: 403 pc += (A >= X) ? pc->jt : pc->jf; 404 continue; 405 406 case BPF_JMP|BPF_JEQ|BPF_X: 407 pc += (A == X) ? pc->jt : pc->jf; 408 continue; 409 410 case BPF_JMP|BPF_JSET|BPF_X: 411 pc += (A & X) ? pc->jt : pc->jf; 412 continue; 413 414 case BPF_ALU|BPF_ADD|BPF_X: 415 A += X; 416 continue; 417 418 case BPF_ALU|BPF_SUB|BPF_X: 419 A -= X; 420 continue; 421 422 case BPF_ALU|BPF_MUL|BPF_X: 423 A *= X; 424 continue; 425 426 case BPF_ALU|BPF_DIV|BPF_X: 427 if (X == 0) 428 return 0; 429 A /= X; 430 continue; 431 432 case BPF_ALU|BPF_AND|BPF_X: 433 A &= X; 434 continue; 435 436 case BPF_ALU|BPF_OR|BPF_X: 437 A |= X; 438 continue; 439 440 case BPF_ALU|BPF_LSH|BPF_X: 441 A <<= X; 442 continue; 443 444 case BPF_ALU|BPF_RSH|BPF_X: 445 A >>= X; 446 continue; 447 448 case BPF_ALU|BPF_ADD|BPF_K: 449 A += pc->k; 450 continue; 451 452 case BPF_ALU|BPF_SUB|BPF_K: 453 A -= pc->k; 454 continue; 455 456 case BPF_ALU|BPF_MUL|BPF_K: 457 A *= pc->k; 458 continue; 459 460 case BPF_ALU|BPF_DIV|BPF_K: 461 A /= pc->k; 462 continue; 463 464 case BPF_ALU|BPF_AND|BPF_K: 465 A &= pc->k; 466 continue; 467 468 case BPF_ALU|BPF_OR|BPF_K: 469 A |= pc->k; 470 continue; 471 472 case BPF_ALU|BPF_LSH|BPF_K: 473 A <<= pc->k; 474 continue; 475 476 case BPF_ALU|BPF_RSH|BPF_K: 477 A >>= pc->k; 478 continue; 479 480 case BPF_ALU|BPF_NEG: 481 A = -A; 482 continue; 483 484 case BPF_MISC|BPF_TAX: 485 X = A; 486 continue; 487 488 case BPF_MISC|BPF_TXA: 489 A = X; 490 continue; 491 } 492 } 493 } 494 495 #ifdef KERNEL 496 /* 497 * Return true if the 'fcode' is a valid filter program. 498 * The constraints are that each jump be forward and to a valid 499 * code. The code must terminate with either an accept or reject. 500 * 'valid' is an array for use by the routine (it must be at least 501 * 'len' bytes long). 502 * 503 * The kernel needs to be able to verify an application's filter code. 504 * Otherwise, a bogus program could easily crash the system. 505 */ 506 int 507 bpf_validate(f, len) 508 struct bpf_insn *f; 509 int len; 510 { 511 register int i; 512 register struct bpf_insn *p; 513 514 for (i = 0; i < len; ++i) { 515 /* 516 * Check that that jumps are forward, and within 517 * the code block. 518 */ 519 p = &f[i]; 520 if (BPF_CLASS(p->code) == BPF_JMP) { 521 register int from = i + 1; 522 523 if (BPF_OP(p->code) == BPF_JA) { 524 if (from + p->k >= len) 525 return 0; 526 } 527 else if (from + p->jt >= len || from + p->jf >= len) 528 return 0; 529 } 530 /* 531 * Check that memory operations use valid addresses. 532 */ 533 if ((BPF_CLASS(p->code) == BPF_ST || 534 (BPF_CLASS(p->code) == BPF_LD && 535 (p->code & 0xe0) == BPF_MEM)) && 536 (p->k >= BPF_MEMWORDS || p->k < 0)) 537 return 0; 538 /* 539 * Check for constant division by 0. 540 */ 541 if (p->code == (BPF_ALU|BPF_DIV|BPF_K) && p->k == 0) 542 return 0; 543 } 544 return BPF_CLASS(f[len - 1].code) == BPF_RET; 545 } 546 #endif 547
Indexes created Tue Sep 30 10:09:55 GMT 2025